Embodiments of the present application relate generally to registering two or more data sets, generally for use in clinical applications. Particularly, certain embodiments relate to identifying differences between an output from an imaging subsystem with that of a tracking subsystem automatically.
Minimally invasive surgery (“MIS”) may involve surgery performed by making relatively smaller entries into the body (as compared to those used in most traditional surgical procedures). Surgeons employing MIS may be able to perform procedures through incisions (or openings called ports) as small as 1/16 of an inch, for example. MIS may also be known as videoscopic surgery, “keyhole” surgery, laparoscopic surgery (laparoscopy), thoracoscopic surgery, or surgical endoscopy.
In order to improve effectiveness of MIS or other procedures such as interventional radiological procedures, it may be helpful to track the position of a surgical tool or an existing object in the patient using a navigation or tracking subsystem. An image of the patient may be generated prior to, and/or during the procedure, for example. Furthermore, clinicians practicing MIS or other procedures may prefer to employ a substantially real-time navigation or tracking system for tracking an objectin the patient prior to, or during the procedure. Consequently, it may be preferable to correlate, and/or register the output from the tracking subsystem with that of the imaging subsystem.
Sets of data acquired by sampling the same scene or object at different times, from different perspectives, or from different systems, may be in non-uniform coordinate systems. Registration may involve the process of transforming the different sets of data into one coordinate system. Registration may be preferable to compare or integrate the data obtained from different measurements, for example. In medical imaging, registration may additionally involve deformable registration to cope with deformable deformations of body parts imaged. Classic registration techniques such as point-pair and surface may not be practical for applications that involve substantially real-time navigation and/or tracking systems. Surgical remote tracking or navigation systems may determine a position and orientation of a navigated or existing object relative to a known reference, for example. A remote tracking or navigation system may be one in which an object for tracking is not physically integrated with the tracking or navigation device itself. During surgery, graphic overlays from the navigation or tracking subsystem may be used in conjunction with a radiological image to represent a surgical tool position and orientation with respect to the patient, for example. The image may be generated before surgery, or at some other time, for example.
One technique that may be used to visually compare the correspondence between the tracking or navigation system and the imaging subsystem may involve leaving a navigated tool in the image when a fluoroscopic image is acquired. System level accuracy may be gauged by observing the position of the tool graphic relative to the position of the actual tool in the image. The degree to which the tool graphic and actual tool image align, may be a good indicator of system accuracy.
However, such a visual test may only illustrate inaccuracies in one plane. To determine a correspondence in other planes may require repeating the test with additional images or tracking positions acquired from different angles. Further, the test may only provide visual feedback, and may not automatically quantify, or improve the misalignment or system accuracy, for example.
Misalignments of tool tracking and tool image may result from a bent or damaged tool or tool interface. Misalignment may also result from system calibrations, system variances, interferences (e.g. metal objects in a patient), and/or the like.
Thus, there is a need for methods and systems that register data from a tracking or navigation system with data from an imaging subsystem automatically. Additionally, there is a need for methods and systems that register data from a tracking or navigation system with data from an imaging subsystem in three or more dimensions. There is a need for methods and systems that register data from a tracking or navigation system with data from an imaging subsystem substantially in real-time. Further, there is a need for methods and systems that assist clinicians while performing procedures, such as MIS procedures.